Liquid crystal display devices are used in a broad range of applications such as mobile phone handsets and other like mobile electronic devices as well as displays for television systems and personal computers. The liquid crystal display device generally delivers excellent visibility when viewed from the front, but has narrow viewing angles.
Various improvements have therefore been made to liquid crystal display devices to increase the viewing angle. One of such improvements is to attach a light-diffusion member onto the viewing side of a liquid crystal panel (display medium) so that the light-diffusion member can diffuse the light emitted from the viewing side of the liquid crystal panel (see, for example, Patent Literature 1).
Patent Literature 1 identified below discloses a light-diffusion sheet (light-diffusion member) including a light-diffusion layer having formed therein grooves with a V-shaped cross-section, wherein there is provided a light-absorption layer in a part of each groove. In the light-diffusion sheet, transparent sheets made primarily of polyethylene terephthalate (PET) are disposed, one on the light-incident side of the light-diffusion layer and another on the light-emitting side thereof. In this configuration, part of the light perpendicularly incident from the light-incident side to the light-diffusion layer undergoes total reflection on the wall faces of the grooves before being emitted in a diffused state from the light-emitting side.
To totally reflect light on the wall faces of the grooves in the light-diffusion sheet, there is preferably a large difference in refractive index between the interior and exterior of the grooves. Because the light-diffusion sheet has a space (air layer) between adjacent grooves, the refractive index difference can be maximized between the transparent sheet (high refractive index) and the air layer (low refractive index).